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This is the 4th in a series of posts on the water quality of Missouri’s surface waters. The first post discussed terms and introductory material about the state’s surface waters. The second and third posts focused on trends in the assessed water quality of the state’s classified streams and lakes. This post focuses on stream impairment in 2014, and its causes (I’m using the word “impaired” for what the Missouri Department of Natural Resources calls “non-support”).

Impairment might mean that the water is unsafe, or it might not. For instance, too much bacteria or lead in the water would make the water unsafe. On the other hand, too much weedy material in the water can make water unpleasant to swim in, or it can give drinking water an unpleasant taste, but it doesn’t necessarily make either unsafe.

Table 1. Source: Missouri Department of Natural Resources 2015.

Missouri’s streams were used for a variety of purposes. Impaired streams may not have been impaired for all uses, but for only some. Table 1, shows the number of classified stream miles used for each use category, the number of miles assessed, and the number of miles impaired. In the table, Whole Body Contact Rec. – A (WBC-A) indicates designated or known swimming areas, Whole Body Contact Rec. – B (WBC-B) indicates areas other areas where recreational whole body contact with the water occurs.

The the number of stream miles used varied from purpose to purpose. The most widespread uses were Aquatic Life & Fish Consumption, Livestock Watering, and WBC-B. Relatively few miles were used for Drinking Water Supply or Industrial. Interestingly, for some uses, only a very small fraction of miles were assessed. For instance, only 11% of the stream miles used for Livestock and Wildlife Watering were assessed, and a tiny 6% of the miles used for Industrial purposes.

Figure 1. Data source: Missouri Department of Natural Resources 2015.

Figure 1 shows the data in the last two columns: the percentage total classified stream miles that were assessed as impaired for each use, and the percentage of assessed stream miles that were assessed as impaired for each use. The blue columns show the percentage of total classified miles, the red column shows the percentage of assessed miles.

No stream miles used for Livestock and Wildlife Watering, Drinking Water Supply, and Industrial were assessed as impaired for those purposes. On the other hand, 85% of assessed stream miles used for WBC-B were impaired for that purpose, 39% of assessed stream miles used for WGC-A were impaired for that purpose, and 35% of of assessed stream miles used for Aquatic Life & Fish Consumption were impaired for that purpose.

Table 2. Data source: Missouri Department of Natural Resources 2015.

Table 2 shows the problem causing of the impairments. There were 22 of them, but the first thing to note is that the list sums to only 5,351 miles. Even if one assumes that there was no overlap between categories, which seems highly unlikely, the list only accounts for only 51% of the total assessed stream miles, meaning that the cause of the other 49% is undocumented. Some of the problems, like bacteria, mercury, lead, zinc, and cadmium, can directly impact human and animal health. Others, like low dissolved oxygen, and temperature, affect the ability of the water to support life.

The bacteria referenced (fecal coliform and E. coli) come from animal waste. Sometimes the contamination comes from livestock, but often it comes from human waste. Waste treatment facilities, be they sewage treatment districts or individual septic tanks, discharge improperly treated waste into streams. Stream eventually cleanse themselves if the bacterial load is not too large, but the water is contaminated for miles downstream.

Table 3. Data source: Missouri Department of Natural Resources 2015.

Table 3 shows the source of the problems causing the impairments. Again, the first thing to notice is that the list sums to only 5,344 miles. As above, even if one assumes that there was no overlap between categories, the list accounts for only 51% of total assessed stream miles, and the source of the remaining 49% is undocumented. Beyond that, the leading two categories in the list are Not Specified, Nonpoint, and Not Specified, Source Unknown.

Atmospheric Deposition was the leading known source of stream impairment. Readers of this blog encountered atmospheric deposition in the post on Heavy Metals in the Big River. There, I wrote about material from mine waste piles being blown by the wind into the Big River. Even more, however, most of the problem we have with mercury toxicity in fish comes from atmospheric deposition. Coal contains trace amounts of mercury. When coal is burned in power plants, the mercury is vented up the flue into the atmosphere. Over time it settles out of the atmosphere into bodies of water, or it settles onto the land, where rain washes it into bodies of water. There, it is ingested by tiny organisms, which are then eaten by fish.

There is a disconnect between Tables 2 and 3. In Table 2, the largest contaminant type was Bacteria. In Table 3, the largest known source of contamination was Atmospheric Deposition. Bacteria are not deposited into streams by the atmosphere. Municipal Point Source was the second leading known source of contamination, and that should probably be read as indicating (mostly) sewage treatment discharge. But in addition, some (much?) of the bacterial contamination probably came from untraceable individual septic systems in the Not Specified sources of contamination.

Of the 20 contamination sources that are known, the top 7 are all human caused, and only 2 are not directly related to human activities. We are the ones causing impairment to the streams, not nature.

(A word about the availability of the Missouri Water Quality Reports. As of 5/1/2016, reports for 2002, 2004, 2006, 2008, 2010, 2012, and 2014 are available on the Department of Natural Resources, Water Protection Website. Though the 2014 report is dated April 24, 2014, it was not available on the website until much later. The report for 2016 is not yet available, and may not be for many months.)